* Make cat in test/standalone/simple working again

- Fixes:
    zig/0.15.1/lib/zig/std/Io/Writer.zig:939:11: 0x1049aef63 in sendFileAll (nclip)
        assert(w.buffer.len > 0);
- because we are no using non zero buffers for stdout - "do not forget to flush"

* replace std.fs with fs because we are already importing it